No India visa or transit visa required, just head to the transfer desk and pick up your AI263 boarding pass if you don't have one (which I didn't, UA, nor NH could print my boarding pass). You will go thru security once. You will remain onboard the plane at TRV prior to MLE so its not a layover nor a stopover. The TRV security will do an onboard sweep while you remain in your seat and you will need to confirm your carryon or handbag if you have either or both. Enjoy your trip!